JoVE Encyclopedia of Experiments
Microbiology
0 views • 2:43 min • February 2nd, 2026
Begin with a selective nutrient agar plate supplemented with blood containing RBCs.
Streak Staphylococcus aureus (S.aureus), a Gram-positive pathogenic bacterium, onto the agar and incubate.
During incubation, bacteria utilize nutrients, grow, and form colonies.
S. aureus secretes hemolysin, a pore-forming toxin that lyses the RBCs in the agar and produces clear, transparent zones around colonies, indicative of hemolysis.
Select a hemolytic colony, inoculate it into a nutrient broth, and incubate under rotating conditions to support bacterial growth.
Using a spectrophotometer, measure optical density (OD) to determine bacterial concentration.
Based on the OD reading, transfer an aliquot into a fresh nutrient broth to dilute the cells, and incubate in a water bath with shaking.
Measure the OD at regular intervals.
An OD near 0.8 indicates that the bacteria have reached the exponential growth phase with uniform physiology.
This hemolytic S. aureus is ready for host-pathogen interaction studies.
Begin by streaking S.aureus strains of interest on blood agar plates from a frozen glycerol stock and incubating the plates at 37 degrees Celsius for 16 to 24 hours to confirm their hemolytic phenotypes
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